$-9de - 9df - 6d + 1 = -4e + 2$ Solve for $d$.
Answer: Combine constant terms on the right. $-9de - 9df - 6d + {1} = -4e + {2}$ $-9de - 9df - 6d = -4e + {1}$ Notice that all the terms on the left-hand side of the equation have $d$ in them. $-9{d}e - 9{d}f - 6{d} = -4e + 1$ Factor out the $d$ ${d} \cdot \left( -9e - 9f - 6 \right) = -4e + 1$ Isolate the $d$ $d \cdot \left( -{9e - 9f - 6} \right) = -4e + 1$ $d = \dfrac{ -4e + 1 }{ -{9e - 9f - 6} }$ We can simplify this by multiplying the top and bottom by $-1$. $d= \dfrac{4e - 1}{9e + 9f + 6}$